How do we check whether our lens is effected by fungus?Some of friend told me that at the rear end of the lens we need to torch light and at the same time we have to check from the front end..Can we do it this way or is there any better way to check before giving it for service?Please shed some light on this..

Unless I was selling a lens I wouldn't even bother to check unless I thought there was a problem with images taken with the lens. And if the lens looks perfectly transparent when you shine a light through it then you are set. If in doubt you could always compare the transparency with a known good lens. But whatever you do don't be tempted to use the Sun as your bright light source if you value your eyesight!!!

Just look in normal light. If you see anything on the lens surfaces (internal or external) that can't be explained by dust or other dirt, it could be fungus. Once it sets in, it has an organic pattern to it. You don't need any particular light as long as you can see.